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Biomedical subjects

D R Wilson

Publications and source records attributed to D R Wilson.

At least 181 records · Page 10Linked to original sources
PubMed1976

Cross-circulation study of natriuretic factors in postobstructive diuresis.

To study the role of circulating natriuretic factors in the postobstructive diuresis that occurs after relief of bilateral, but not unilateral ureteral ligation, cross-circulation was carried out between normal recipient rats and donor rats have either 24-h bilateral (BUL) or unilateral (UUL) ureteral ligation. With BUL donors, there was a rapid marked increase in sodium and water excretion in the recipient rats, sustained for 80-140 min, with a peak approximately 10 times control values. With UUL donors, no significant natriuretic response occurred. Changes in glomerular filtration rate, renal plasma flow, blood pressure, hematocrit, or circulating levels of aldosterone or Pitressin did not explain the diuresis-natriuresis produced by cross-circulation with BUL donors. Differences in the intrinsic renal damage produced by bilateral as compared to unilateral ureteral obstruction did not appear to account for this response, since UUL donors given an acute urea load and urine reinfusion caused a similar diuresis-natriuresis. Moreover, normal donor rats given a urea load also caused a diuresis-natriuresis nearly equal to that produced by BUL rats, and the relationship between increased urea excretion and sodium excretion or urine flow in the recipients was not different in the two groups. Total urine reinfusion for 3 h in donor rats produced a significant, although less marked, diuresis-natriuresis in recipient animals, with only a slight elevation of the blood urea nitrogen level, much less increase in urea excretion rate, and no significant relationship between urea excretion and sodium excretion or urine flow. The results indicate that potent natriuretic factors, which act by decreasing the tubular reabsorption of sodium and water, are present in the blood of rats with bilateral, but not unilateral, ureteral ligation. High blood and urine urea levels appear to be the factors responsible for the marked natriuresis-diuresis occurring in normal rats during cross-circulation with BUL donors, although suggestive evidence of other natriuretic factors in urine reinfused intravenously was also obtained. The data suggest that urea osmotic diuresis is an important mechanism for determining the striking difference between the postobstructive diuresis observed after relief of bilateral as compared to unilateral ureteral ligation.

Adenosine Triphosphatases↗
PubMed1976

The role of the medullary collecting ducts in postobstructive diuresis.

Medullary collecting duct function was studied by direct microcatheterization techniques in rats undergoing postobstructive diuresis. Significant net addition of water and sodium to the duct was demonstrated during postobstructive diuresis after relief of 24-h bilateral ureteral ligation. This striking abnormality in function was associated with reduced delivery of sodium and water to the collecting duct compared to sham-operated controls. To examine the role of circulating factors in this phenomenon, another group of rats was studied that underwent 24 h of total urine reinfusion into the femoral vein. Natriuresis and diuresis were similar to the postobstructive group, but absolute collecting duct reabsorption of sodium and water was normal. The natriuresis and diuresis in rats with urine reinfusion resulted from increased delivery of fluid and sodium to the medullary collecting duct. A third group of rats was studied with 24-h unilateral ureteral ligation as well as urine reinfusion from the contralateral normal kidney. Without urine reinfusion there was no diuresis-natriuresis but with urine reinfusion the diuresis and natriuresis after relief of unilateral obstruction was similar to that after relief of bilateral obstruction. Moreover, net addition of sodium and no significant water reabsorption were demonstrated in the medullary collecting duct of such animals. The results indicate that (a) the medullary collecting duct is the critical nephron segment affected by ureteral obstruction, since postobstructive diuresis occurred despite reduced delivery of fluid from the more proximal nephron; (b) the net addition of sodium to the medullary collecting duct observed during postobstructive diuresis is probably a direct effect of obstruction, since it was found during postobstructive diuresis after relief of bilateral or unilateral ureteral ligation, but not with urine reinfusion alone; and (c) blood-borne factors are important in the development of postobstructive natriuresis and diuresis, and probably act by increasing the fraction of filtered sodium and water delivered from the proximal and distal tubule to the collecting duct.

Absorption↗
PubMed1976

Defective triglyceride removal in lipemia associated with peritoneal dialysis and haemodialysis.

Plasma lipids were measured in 78 uremic patients receiving either chronic peritoneal dialysis or haemodialysis. Type IV hyperlipemia was found in 60% of patients. The lipid level was not influenced by dietary habits or patient's age. Patients on chronic peritoneal dialysis had a significantly higher and more sustained hyperlipemia than the patients on haemodialysis. Triglyceride turnover studies showed that all patients, regardless of the type of dialysis or lipid level, had impaired triglyceride removal as the cause of this lipemia. This defect in triglyceride metabolism was only partially corrected by increasing the efficiency of the dialysis.

Adult↗
PubMed1975

Nephron functional heterogeneity in the postobstructive kidney.

The purpose of this study was to determine the distribution of nephron filtration rates between superficial and juxtamedullary nephrons (S/J ratio) in kidneys studied immediately after relief of 24 hr total obstruction (acute) and after relief of prolonged partial obstruction (chronic). Injection of 14C-ferrocyanide and microdissection (modified Hanssen's technique) was used to provide an index of superficial and deep nephron glomerular filtration rate (GFR), and standard clearance determinations were done. In normal kidneys S/J ratio of 14C content (nephron GFR) was 0.73 plus or minus 0.03, a value similar to those obtained by other workers. After relief of acute obstruction, nephron GFR was too low for accurate measurement in 22% of superficial and 13% of deep nephrons. The mean S/J ratio of 14C content was similar to control, being 0.67 plus or minus 0.07, with only three of seven kidney showing loss of the normal S/J ratio. Since redistribution of nephron GFR was an inconsistent finding, while marked diuresis and natriuresis occurred in all rats, it appears that redistribution of nephron GFR is not an important factor in the phenomenon of postobstructive diuresis. After relief of chronic obstruction, diuresis and natriuresis were less marked but the mean S/J ratio of 14C content was 0.95 plus or minus 0.11, and in the majority of kidneys (six of eight), there was loss of distinction between superficial and deep nephron GFR. This redistribution of nephron function after relief of chronic, rather than acute, obstruction may be due to the more severe structural damage to the renal medulla of such kidneys and, although not responsible for postobstructive diuresis, it may be important in the diminished capacity of the chronically hydronephrotic kidney to conserve salt and water.

Acute Disease↗
PubMed1975

Mechanisms of post-obstructive diuresis in the solitary hydronephrotic kidney of the rat.

1. In order to clarify further the phenomenon of post-obstructive diuresis, clearance and micropuncture experiments were done before and after relief of partial ureteral obstruction in rats with a solitary hydronephrotic kidney. 2. Glomerular filtration rate, urine flow and sodium excretion increased markedly, whereas surface nephron glomerular filtration rate increased only slightly and intratubular pressure, proximal and distal tubular water reabsorption did not change significantly. Decreased tubular reabsorption in deeper nephrons and collecting ducts appeared to be of major importance in the post-obstructive diuresis after relief of chronic obstruction. 3. In order to examine further the distinctive functional characteristics of the chronically hydro-nephrotic kidney, the results were compared with control rats having a solitary normal kidney or a solitary remnant kidney with an intact renal medulla. Urine flow rate and sodium excretion were higher and urine osmolality was lower (P less than 0-01) in post-obstructive kidneys when compared with either control group. There were no differences in glomerular filtration rate or surface nephron function which could account for the greater diuresis and natriuresis from the hydronephrotic kidney, thus confirming the importance of an abnormality in deep nephron or medullary function in post-obstructive diuresis. 4. There was a greater diuresis in post-obstructive rats with a marked increase in blood urea concentration. Water reabsorption in the distal nephron was decreased in such animals, as well as in urea-loaded rats with a remnant kidney, indicating the probable mechanism by which urea diuresis potentiates the phenomenon of post-obstructive diuresis.

Animals↗
PubMed1975

Identification and successful treatment of congenital microfistulas with the aid of directional Doppler.

Hitherto unidentifiable and therefore untreatable congenital microfistulas were detected with the aid of continuous-wave directional Doppler and a fine-beam pencil probe. The microfistulas formed part of the Klippel-Trenaunay (K-T) syndrome. The management of one case is reported in detail and in three others salient features are touched upon. Careful clinical and radiological examination failed to demonstrate any arteriovenous microfistulas. When Doppler ultrasound scanning was carried out, two discrete fistulas were discovered. Their extent and direction were mapped out accurately. Incisions were made directly over the markings displaying a pulsating capillary tuft of vessels. Further dissection exposed a feeding arteriole which was less than 1 mm. in diameter. Excision of the vascular malformations resulted in the cure of the patient. In another patient with the K-T syndrome in whom a cutaneous hemangioma involved the whole lower limb, in spite of a thorough and systematic search with a Doppler, no microfistulas could be demonstrated. It is suggested that all patients suffering from the K-T syndrome should be examined by Doppler ultrasound in the hope that microfistulas which elude radiodiagnostic techniques might be detected and treated surgically.

Adult↗
PubMed1975

The effect of thiazide diuretics on carbohydrate-induced calciuria in patients with recurrent renal calculi.

Thiazide diuretics could have a beneficial effect in the prevention of recurrent renal calculi by decreasing the exaggerated calciuria which follows carbohydrate ingestionin patients who form calcium oxalate stones. The calciuric response to 100Gm. or oral glucose was studied in 21 patients with recurrent calcium stones before and after 6 months of hydrochlorothiazide therapy...

Adult↗
PubMed1975

Noninvasive assessment of aorta-coronary saphenous vein bypass graft patency using directional Doppler.

Noninvasive monitoring of patency of aorta-coronary bypass grafts can be achieved with reasonable accuracy using the continuous wave directional Doppler and a pencil probe. The character of the graphic record and the auditory signal generated by the flow through these new vessels perfusing the myocardium are distinctive because of both the pattern of flow and also the fixed and relatively immobile position of these grafts in the anterior mediastinum. A total of 226 aorta-coronary bypass grafts were monitored in the first postoperative week: 82 to the right coronary artery (RCA), 90 to the left anterior descending (LAD), and 56 to the circumflex and lateral ventricular branches. Interpretation of patency in these latter vessels was consistently unreliable and was abandoned early in the study. This unreliability was probably due to their short superficial course and their juxtaposition to the aorta and the pulmonary artery. In contrast, flow through grafts to the RCA and the LAD could be established in approximately 90%. Of 82 grafts to the RCA, flow could not be detected in four (5%) and was doubtful in two (2%). In 90 grafts to the LAD, no flow was observed in four (4%) and was doubtful in five (6%). Comparing noninvasive Doppler results with angiography in 34 grafts, no false negatives were found, but there were two or 10% false positives. Flow characteristics in a functioning internal mammary implant were also found to be quite different from those in an intact opposite mammary artery. This form of monitoring requires some practice and experience but is quick, cheap and noninvasive. It offers an acceptable degree of accuracy in monitoring aorta-coronary bypass grafts to the RCA and the LAD when the conduits are in the anterior mediastinum.

Coronary Artery Bypass↗
PubMed1974

Reconstructive vascular surgery for renovascular hypertension.

Forty-six patients who underwent renal artery repair for presumptive renovascular hypertension are presented. Preoperative investigation included a rapid sequence IVP, a high quality angiogram and split function studies, as well as renin assays of renal venous blood in the more recent cases. Atherosclerosis was the causative pathological lesion in 60% of the patients, with fibromuscular dysplasia or miscellaneous causes of stenosis accounting for the remaining 40%.Surgical correction was usually obtained by bypass grafting (57%). Hypertension was cured or significantly improved in 36 patients (78%).Optimal results are dependent upon complete preoperative investigation and surgical repair of all the stenotic areas.

Adult↗